Diseases and Environmental Factors of the Pinyon-Juniper Communities

The pinyon-juniper woodland is the dominant ecosys­ tem in Utah. While it is a very successful ec()system, it is not without its disease problems. The limiting soil nutrients appear to be nitrogen, phosphorous, and potassium. Temperature and moisture gradients are limiting factors in the growth of pinyon and juniper. Juniper decline appears to be related to drought and tempera­ ture stress and increased salts. A number of pathogens occur on Pinus edulis and Juniperus osteosperma. The most frequent patho­ gens on junipers are the rust fungi. Mistletoe was more common on pinyon than juniper but mistletoe infection has an impact on both. The pinyon-juniper woodland is a widespread vegeta­ tion type in the Southwestern United States that is esti­ mated to cover from 40 to 50 million hectares (Allred 1964; Tausch and Tueller 1990). The pinyon-juniper vegetation provides a source of fuel, building materials, charcoal, pine nuts, Christmas trees, and folk medicines (Cronquist and others 1972; Gallegos 1977; Hurst 1977; Lanner 1975; Tueller and others 1979). About 80 percent of the acreage is grazed by livestock and wildlife (Bunderson and others 1986b; Clary 1975). In Utah, this ecosystem is a large component (62,705 km2 or 28.6 percent) of the vegetation (Kuchler 1964). The pinyon-juniper woodlands are valued for their watershed, aesthetic, and recreational values (Gifford and Busby 1975). The pinyon-juniper woodlands also have a range of diseases. They range from non-pa thogen types (environmental factors) to specific pathogens. Both types will be discussed in this paper. The purpose of this manuscript is to review the non-pathogenic factors and pathogens present in pinyon-juniper woodlands.